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| Keywords: Triskele-hollow-triangle.png Triple spiral or spiral triskelion symbol with hollow triangle in center Inspired by various Celtic decorative motifs but this version is constructed from mathematical Archimedean spirals For other versions of the spiral triskelion or triple-spiral symbols see Image Triskele-Symbol-spiral-five-thirds-turns png Image Triple-Spiral-Symbol-filled png Image Triple-Spiral-Symbol-4turns-filled png Image Triskele-Symbol-spiral png or Image Triple-Spiral-Symbol png For wheeled forms of the triple-spiral see Image Wheeled-Triskelion-basic png Image Roissy triskelion iron ring signet png Image Triple-spiral-wheeled-simple png or Image Triskelion-spiral-threespoked-inspiral png For versions of a triple-spiral labyrinth see Image Triple-Spiral-labyrinth png and Image Triple-Spiral-labyrinth-variant png Generated by means of the following PostScript code <pre> /archimdouble PostScript program to display an Archimedean spiral by approximating it with Bezier curves Can display a double spiral two spirals rotated by 180 degrees with respect to each other Parameters centerx horizontal coordinate of center of spiral centery vertical coordinate of center of spiral rotf degrees to rotate /sepwid 110 def width separating successive turnings of spiral half this if double spiral is selected /incrm 15 def insert a curve point after this number of degrees /sweeps 2 def number of 360 degree turnings to show /double 1 def change to 0 to display single spiral Procedures /pi 3 1415926535898 def/radians 57 295779513082 def /sepwid sepwid pi div 2 div def gsave centerx centery translate rotf rotate /aspiral /prevbezy 0 def 0 0 moveto 0 incrm sweeps 360 mul 7 dup repeat phase add cos/costh exch def phase add sin/sinth exch def costh mul radians div/thcosth exch def sinth mul radians div/thsinth exch def thcosth sepwid mul/x exch def thsinth sepwid mul/y exch def /slope sinth thcosth add costh thsinth sub div def sinth 0 gt sinth 0 eq costh -1 eq and or /flag -1 def /flag 1 def ifelse /A exch def A 49 29348 lt A 180 gt A 196 273450852 lt and A 360 gt A 368 8301 lt and A 540 gt A 545 9907 lt and A 720 gt A 724 5217 lt and A 900 gt A 903 6281968 lt and or or or or or /flag flag neg def if incrm sub 3 dup repeat phase add cos sepwid mul mul radians div /prevx exch def phase add sin sepwid mul mul radians div /prevy exch def incrm add 3 dup repeat phase add cos sepwid mul mul radians div /nextx exch def phase add sin sepwid mul mul radians div /nexty exch def /prevdist x prevx sub dup mul y prevy sub dup mul add sqrt pi div def /nextdist x nextx sub dup mul y nexty sub dup mul add sqrt pi div def /normaliz slope slope mul 1 add sqrt def 0 eq /prevbezx phase cos nextdist mul def prevbezx prevbezy x 1 flag mul normaliz div prevdist mul sub y slope flag mul normaliz div prevdist mul sub x y curveto /prevbezx x 1 flag mul normaliz div nextdist mul add def /prevbezy y slope flag mul normaliz div nextdist mul add def ifelse for stroke x y moveto x 1 flag mul normaliz div nextdist mul pi mul const mul add y slope flag mul normaliz div nextdist mul pi mul const mul add lineto stroke def /phase 0 def/const 3 def aspiral If different sweeps parameter for second spiral define here /sweeps 1 67 def double 0 ne /phase 180 def/const 3 945 def aspiral if grestore def gsave 600 0 translate - 5 5 scale -3 685 rotate /centerx 221 5 def/centery 550 def/rotf -39 989 def archimdouble /centerx 789 833 def/centery 550 def/rotf 80 011 def archimdouble /centerx 505 667 def/centery 1042 19089 def/rotf 200 011 def archimdouble grestore 5 setlinewidth 350 167 264 925 moveto 377 085 399 621 lineto 246 976 355 585 lineto closepath stroke showpage EOF</pre> 2005 AnonMoos Pagan Barnstar png Triskele-hollow-triangle svg Triple spiral Celtic graphic ornaments Archimedean spirals Images with PostScript source code | ||||
